1. Field of the Invention
The present invention relates to a measuring method and apparatus for measuring distribution of sensitivity. More particularly, the present invention relates to a measuring method and apparatus for measuring distribution of sensitivity of a photo sensor both with high precision and with great ease.
2. Description Related to the Prior Art
A photo sensor of a reflection type is known for example in JP-A 2001-312688. The photo sensor includes a light projector and a photoreceptor. The light projector projects light or a beam for photoelectric detection. The photoreceptor receives and detects light reflected by an article to be detected after emission from the light projector. The photo sensor is used as a reader for reading an information code formed on a winder core which is used in a photographic printer as a core of a roll.
If the photo sensor is used, it is necessary to adjust positioning in the attachment, electric correction of outputs and other calibration for the purpose of optimizing the sensitivity to light. It is likely that a manufacturing cost will be higher because of additionally complicated operation required for the adjustment and correction.
To solve such a problem, there is a light detecting device of JP-A 2001-175799 including an amplifier, an A/D converter, a microcomputer and a resistor circuit. The amplifier amplifies an output of the photoreceptor. The AID converter converts the output of the amplifier into a digital signal. The microcomputer changes an output level of the photoreceptor according to data of the digital signal. The resistor circuit is controlled by the microcomputer, for varying the output level of the photoreceptor at a point before the amplifier.
Also, testing of sensitivity of a photo sensor is known, for example, U.S. Pat. No. 5,473,167 (corresponding to JP-A 8-050094).
Although the S/N ratio of the photo sensor can be increased according to JP-A 2001-175799, a characteristic of the photo sensor cannot be found in a detailed manner. It is likely to use the light detecting device at not very high sensitivity of photo sensor. This is a structure unsuitable for the use in detection with higher precision.